Ever since human beings first began to organise into social groups there has been some kind of exchange market. Filthy lucre in one form or another has insisted on creeping in to dominate our social fabric. The reality is that our modern capitalist metropolises based on physical money are simply the concrete evolutions of our Cro-Magnon days, when the currency was fish, wives or finely crafted stone, with an unexpected detour through Holland during the tulip-mania economic bubble of the 1630s.

Georg Simmel, the early-20th-century German sociologist, described money this way: humans have a natural tendency to create unnatural hierarchies that predicate the need for haves and have-nots because, ironically, they serve a very useful role in social cohesion. They force us to interact with one another, and give us insight into who we're dealing with and how the exchange process will play out.

The tokens of our economic systems, Simmel continued, define cultural value both tangibly – with metal discs and pieces of paper – and intangibly: through the exchange of skills and information. Rocks, tulip bulbs and over-priced apartments have also served as tokens in other times. So, regardless of its physical or non-physical properties, the function of money has always been the same: to represent the ideological exchange of value and the attribution of social worth upon something someone else wants.

Money is also a physical hallmark of trust: the banknote that we often incorrectly think of as cash is nothing but an IOU. The bank will "give to the bearer" the value written on the piece of paper when asked. In other words, money is already removed from the realm of the physical: it is a historical and philosophical construct that holds society together. And it has not changed in millennia.

So it's unsurprising that money – as a representative of social value – remains enormously important in the web age, despite our rapid uptake of a technology that has the potential to eradicate the scarcity that defines the rates of exchange. Online, "our property can be infinitely reproduced and instantaneously distributed all over the planet without cost, without our knowledge, without its even leaving our possession," as the internet writer John Perry Barlow put it in a 1992 essay, Selling Wine Without Bottles: The Economy of Mind on the Global Net. But this plenty has not dissolved value; it has shifted it into something more intangible. Still, human nature gets in the way.

We continue to impose worth online, even though we are able to operate and trade an infinite amount for free (once we have satisfied our basic offline needs, like food and shelter). Even in an environment where we don't need to satisfy basic human needs, we insist on imposing calculable value so we can make a buck.

For example, in this system defined by plenty, we seek out impossible rarity and price it accordingly. In virtual communities such as online games, where our online personas have no hunger and no exhaustion, people sell character accounts, piles of virtual currency, game items that have been built up through "click-labour", and even bits of broken code that somehow slipped through the software testing phase, for real money on auction sites such as eBay. There is nothing new in this economic model except the asset that's being exchanged.

But there is a difference. The exchange economies of the web are based upon the actions and relationships that make up our online reputations. Risk is high online due to the potential number of new strangers that we can meet, and the anonymity of the web means that the heuristics we use to figure out if someone is trustworthy or not – including reports from friends, brand recognition, clothing and facial expressions – are virtually impossible to identify in this new digital wild west. Trust has become the pinnacle of virtual currency. It's what people depend upon to function online. It is the source of our reputations in the virtual space. But there is no cash to create the tangible IOU, so we create recommendations engines and ratings systems, and rely on links from friends to get worthwhile information. Trust is money online: it's what we have, and what we have not.

The web really has done very little to transform our social concept of money – if anything, it's made us more aware of its true philosophical underpinnings, and has divorced it from the paper stuff in our wallets. It puts the pound sterling, the dollar and the yen into perspective if people can make a real-life living from buying and selling virtual items for digital platinum pieces. And the idea that people will ascribe worth to things in an environment that doesn't demand it suggests that Simmel's philosophy of money itself has value.